I. Field of the Invention
This invention relates to communications systems and more particularly to the monitoring, operating and controlling of remote equipment in a communication system.
II. Description of the Related Art
Communication systems and, in particular wireless communications networks such as cellular network communication systems, use various equipment throughout their systems to process and maintain the quality of signals carrying user generated information such as text, voice, and video. Equipment located throughout the system which are remotely located from each other are often used to improve signal quality in areas that would otherwise receive a degraded signal or no signal at all or in areas where a signal that is transmitted would be degraded when received. In order to ensure the proper functioning of these communication systems, the remote equipment must be monitored, controlled and operated on a continual basis.
FIG. 1 is a system level diagram of a cellular wireless communications system similar to the Autoplex.RTM. cellular communications system (Autoplex is a registered trademark of Lucent Technologies, Inc.) available from Lucent Technologies, Inc. of Murray Hill, N.J. The Autoplex.RTM. cellular communications system, when configured as a Code Division Multiple Access (CDMA) system, is in compliance with the TIA/EIA/IS-95A communication protocol. The TIA/EIA/IS-95A protocol is a compatibility standard for cellular mobile telecommunications systems that dictates how information is to be transmitted, processed and received in a communication system that uses a Code Division Multiple Access scheme or wideband spread spectrum mode of operation. FIG. 1 depicts communication center 2 connected to a telephone network such as public switch telephone network (PSTN) 4. Communication center 2, commonly referred to as a Mobile Switching Center (MSC), is connected to network 4 via trunk line 6 which carries information between network 4 and communications center 2. Communications center 2 is also connected to communication sites 8, commonly referred to as cell sites or base stations, throughout the cellular network. Each communication site 8 is located in a particular cell 10. Communications between communication center 2 and communication sites 8 is provided by communication channel 12 which is typically a trunk line. Each cell 10 is represented by a hexagon which is a symbolic representation of the geographic terrain or particular physical area that is being served by a communication site. That is, each cell 10 has a communication site 8 which communicates with user stations or mobile stations within that cell via a user channel such as a wireless user channel.
Also, system information is conveyed between communication site 8 and the user stations or between communication site 8 and communication center 2. The system information, commonly referred to as overhead information includes information such as a request by a mobile station for assignment of a user channel, information concerning the status of a mobile station, user channel assignment by communication site 8, and communications with communication center 2 regarding handoffs between cells. System information is transmitted and received using one or more overhead or system channels that are separate from the user channels. The system channel and the user channels will be discussed in greater detail below. For clarity, in the figures discussed below, channels which typically carry user information are depicted with solid lines while channels that typically carry system information are depicted with broken lines.
FIG. 2 is a detailed diagram of a particular cell of a CDMA based cellular communication system. The particular cell being shown is that of the Autoplex.RTM. cellular communications system as currently configured and designed. System information is conveyed over system channel 24 of communication channel 12 between communication center 2 and communication site 8. User information is conveyed over user channel 22 of communication channel 12 between communication center 2 and communication site 8. Communication center 2 is known as the Autoplex.RTM. cellular communications system Control Complex which has digital switch 14 that interfaces to PSTN 4 and a call processing module 16 which in turn interfaces with an Operation Administration and Maintenance (OA&M) module 18 and Maintenance Cathode Ray Tube (MCRT) 20. Call processing module 16 processes, packages and routes incoming and outgoing user and system information in accordance with the IS-95A protocol and any other protocol developed for the system. Call processing module 16 relays incoming user information to PSTN 4 via trunk line 6. Incoming system information is recognized as such by call processing module 16 which routes such information to OA&M module 18. OA&M module 18 processes the received system information so that the information is displayed on MCRT 20. Outgoing user information originating from PSTN 4 is relayed by call processing module 16 to communication site 8 over user channel 22 of communication channel 12. Outgoing system information originates from call processing module 16 or OA&M module 18 which transfers such information to call processing module 16. Outgoing system information may also originate from call processing module 16. Call processing module 16 formats and packages the system information in accordance with the IS-95A standard and then transmits the information over system channel 24 of communication channel 12. Also, communication center 2 uses the system channel information to monitor, operate or control various equipment located at communication site 8. User information is conveyed between communication site 8 and the user stations 28 over wireless user channel 26. User communication link 26 is a full duplex wireless channel which carries user information between communication site 8 and user station 28.
In some cells of a wireless communication system, coverage is limited by structures, such as tall buildings, mountain ranges and other physical obstacles that block or interfere with communication signals. This problem may be addressed by providing remote units 30 that are repeaters. Remote unit 30, configured as a repeater, relays communication signals between communication site 8 and a user or users in an area that cannot be covered adequately by direct communication with communication site 8. The remote unit receives the communication signal from the communication site 8 and performs functions such as noise reductions and amplification on the received signal, and then retransmits or relays the signal to a user in the area that has difficulty receiving signals directly from communication site 8. Similarly, in an area which has difficulty in transmitting a signal directly to communication site 8, the signal is transmitted to a remote unit configured as a repeater which in turn relays the signal to communication site 8. The repeater relays both user information and system information to communication site 8 and user station 28.
System information between user stations 28 and communication site 8 is conveyed over a system communication link, commonly referred to as an overhead channel, that is separate from user communication link 26. The system communication link comprises two simplex channels referred to as paging channel 36 and access channel 38. Paging channel 36 is used by the communication site 8 to transmit system information to user stations 28 and remote units 30 configured as repeaters. User stations 28 and remote units configured as repeaters use access channel 38 to transmit system information to communication site 8. The system information is conveyed over system channel 24 of trunk line 12 between communication site 8 and communication center 2. Thus, user stations 28 have the capability to communicate with communication center 2 over system channels. Also, remote units configured as repeaters, relay system information to user stations 28 over paging channel 36 and relay system information from user stations 28 over access channel 38. Remote units 30, configured as repeaters, do not have the capability of transmitting or receiving system information associated with their operation, monitor or control and thus cannot be monitored by communication center 2.
A typical method used to monitor remote units 30, configured as repeaters, is illustrated in FIG. 3. Remote unit controller 32 monitors and controls remote units 30 through its communication link 34 with communication center 2. Communication link 34 is a two-way link which may be, for example, a telephone link with modems or a dedicated Ethernet link. The information transmitted over link 34 by remote unit controller 32 is received and processed by communication center 2. The information is then relayed over communication channel 12 to communication site 8 which in turn transmits the information over user link 26 to the particular remote unit 30 being monitored. The remote unit that is being monitored acknowledges the reception of the information and, if necessary, transmits a response to controller 32 over user link 26.
Thus, this method utilizes user links 26 in order to monitor the remote units 30. As a result of this configuration, the amount of user links available to users of the system is decreased when remote unit controller 32 is in the process of monitoring remote units 30. An additional disadvantage to this configuration is the limited ability of remote unit controller 32 to have access to any remote unit 30 on an as needed basis. Remote unit controller 32 is simply another user of the system which must compete for available user channels before it can operate, monitor or control remote unit 30.
The TIA/EIA/IS-95A protocol requires that, upon powering up of the system, all user stations 28 (or mobile station) in each cell 10 follow an initialization process represented by the state diagram shown in FIG. 4. For the sake of simplicity, not all the possible state transitions of a user station are shown. Some of the state transitions shown are not discussed herein to any great detail as they are not relevant to the subject matter of this invention; however, all of the state transitions are well known in the art and are part of the TIA/EIA/IS-95A standard. Referring to FIG. 4, upon power up, each user station enters an Initialization State via transition 40. Once the user station has been fully integrated into or registered with the communication system, it enters an Idle State through transition 42. In the Idle State, the user station monitors messages on the paging channel and enters the System Access State through transition 48 when it receives a paging channel message that requires a response. If for some reason, the user station has difficulty in receiving messages over the paging channel, it reenters the Initialization State via transition state 44. In the System Access State, the user station sends messages to the communication site on the access channel. Transition 50 allows the user station to enter the Traffic Channel state which allows the user station to communicate with the communication site over a user link 26.
While in the System Access State, the user stations can respond to requests from the communication center concerning system status and operation via the communication site with a set of pre-defined message formats. The messages are specifically related to user station functions which are recognized as such by the communication center. Also, the user stations can transmit to the communication center a general data message in a message packet formatted in a Data Burst message mode in accordance with the TIA/EIA/IS-95A protocol. The messages formatted in the Data Burst message mode are transmitted over the access channel to the communication site and relayed to the communication center. These data burst messages are not used by the communication center 2 for system operation; they are processed and relayed to PSTN 4 or user stations 28. This message format is used to convey text information, referred to as Short Message Services for Wideband Spread Spectrum System, between user stations. Remote units configured as repeaters do not have the capability to process these messages. These messages are simply relayed on to a user station or to a communication site by the remote unit configured as a repeater. Thus, regardless of the particular mode of system communication being followed by the system, the remote unit configured as a repeater does not have the capability to communicate with the communication center to allow the communication center to operate, monitor and/or control the remote unit.